Method and apparatus for forming fibers



July 17. 1956 c. J. STALEGO METHOD AND APPARATUS FOR FORMING FIBERSFiled July 5, 1951 (Ittomegs United States Patent O METHOD AND APPARATUSFOR FORMING FIBERS Charles J. Stalego, Newark, Ohio, assiguor to OwensCorning Fiberglas Corporation, a corporation of Delaware ApplicationJuly 5, 1951, Serial No. 235,222

19 Claims. (Cl. 18-25) This invention relates to method and apparatusfor forming comparatively fine fibers from heat softenable material andmore especially to the production of fine fibers attenuated from moltenglass and the like.

One of the preferred methodg of forming or producing mineral fibers orfibers from heat softenable material such as glass is to subjectfilaments of heat softenable material to a heating medium usually in theform of a high velocity blast of intensely hot gasses projected from aninternal combustion burner whereby the filaments are continuouslyadvanced into the hot blast where they are attenuated or drawn into veryfine fibers by the velocity of the hot gases emanating from the burner.Filaments of glass or other heat softenable material, usually referredto as primary filaments, especially usable for fiber formation areusually from ten to twenty thousandths of an inch in diameter and areadvanced at a controlled rate into the hottest zone of exhaust or burnedgases from the burner which softens the tips of the primary filaments,the velocity of the hot exhaust gases first drawing the softened tips totapered configurations termed secondary filaments, the latter beingattenuated to comparatively fine fibers, being in the nature ofapproximately two microns in diameter.

It has been found that while fiber attenuation by this method issuccessful under optimum conditions, the operating conditions areextremely critical. For example, the primary filaments must be advancedor fed into the flame of the burner at an accurately determined ratewhere the maximum volume of glass will be attenuated to secure thehighest economy; and, if the filaments are advanced too rapidly or tooslowly, then the attenuation of fibers is not carried on properly. Thesuccessful production of fibers by this method requires that severalfactors such as the temperature of the heating zone, the relativepositioning of the primary filaments and the rate of feed of thefilaments must be correlated and maintained in order to produce uniformfine fibers.

If the combustible mixture varies even in minor amounts in itsconstituent ratios, the temperature of the filament heat zone may alsovary to an extent vitally affecting the attenuation of the glass orother heat softenable material into fibers. Furthermore, a minutevariation in the diameters of the filaments or unit volume of glassbeing fed into the heating and attenuating zone may materially interferewith proper attenuation.

One of the difficulties encountered when the operating factors orconditions are not correlated or functioning in the proper manner isthat the fibers may have minute pellets of glass attached thereto or thepellets may be unattached to fibers, such formation being conventionallyreferred to as hot slugs. Thus if the primary filaments are fed into theflame at too slow a rate for the proper volume of glass to be attenuatedor if the temperature is too high for the amount of glass fed into theheating zone, such slugs or pellets are formed, some being entailed onthe fibers rendering the fiber forming process virtually inoperable. Torestore normal operation, the

2,754,541 Patented July 17, 1956 ice operator must make instant thoughminute correction of the factor or factors responsible for improperattenuation. Any temporary interruption of the normal rate ofattenuation or deviation of the relation of the feed of the primaryfilaments into the blast or lack of correlation of other criticalfactors tends to produce the socalled hot slugs. One of the factorswhich augments the tendency to slugging when optimum conditions are notpresent is the establishment of reduced or differential pressure on thedownstream side of the primary fibers adjacent the lower ends of thefilaments at their entrance to the attenuating zone. This difierentialpressure has the effect of causing the heat softened filament at thestart of attenuation to be moved or biased upwardly and away from thehottest part of the attenuating blast, the net efiiect of which is tocause the fibers being formed to roll or coil up into pellets or slugsadjacent the softened end of the primary filaments in the zone ofreduced pressure. This disrupts fiber formation and results in waste ofglass. a

The present invention embraces a method of minimizing the existence ofunequal pressure or substantially equalizing the pressure adjacent theprimary filaments so as to eliminate the tendency of the heat softenedfilament being attenuated to fibers to move out of the locus of theattenuating forces.

The invention contemplates a method and means of substantiallyequalizing the pressures in the attenuating zone of a fiber attenuatingblast adjacent the fiber forming material entering the blast wherebyattenuation of the fiber forming material may be continuously carried onin a manner securing satisfactorily attenuated fibers.

An object of the invention resides in the establishment of a pressureequalizing medium adjacent the entrance zone of a supply of heatsoften-able fiber forming material into an attenuating blast wherebydisruption of fiber formation and attenuation is avoided.

An object of the invention resides in the provision of means disposed ina zone of normally reduced pressure adjacent the downstream side of afilament of heat softenable material being fed into a material softeningand attenuating zone of an intensely hot, high velocity gaseous blastwhereby the heat softened material forms secondary filaments which aremaintained in the most efiicient attenuating zone of the blast as thesecondary filaments are drawn into fibers.

Another object of the invention resides in a method and arrangement forattenuating fibers from thermofusible material wherein the variousfactors normally correlated to provide optimum operating conditions maydeviate from normal without materially interfering with continuoussatisfactory fiber attenuation.

Still another object is the provision of a method and arrangement ofattenuating fibers from thermofusible fiber forming material by a blastof gas wherein a reduced pressure or partial vacuum existent at one sideof the primary filament of fiber forming material is counteracted,oifset or negated in a manner whereby the locus of movement of thefibers during the attenuation operations is substantially in the core ofthe gas stream of the blast.

Another object is the provision of an arrangement for attenuating fibersfrom glass utilizing a high velocity blast of hot gases wherein theformation of pellets or slugs is reduced to a minimum or substantiallyeliminated.

Still another object of the invention is the provision of a method ofattenuating fibers from heat softenable material wherein the heatsoftened, fiber forming material is maintained in the most efiectivezone of the attenuating gas stream with a minimum of deviation therefromso that a highly efficient and effective fiber attenuation is obtainedand wherein the factors of rate of feed of fiber forming material, thetemperature of the attenuating flame and the like may vary withinconsiderable limits without materially affecting the attenuation offibers.

Further objects and advantages are within the scope of this inventionsuch as relate to the arrangement, operation and function of the relatedelements of the structure, to various details of construction andtocombinations of parts, elements per se, and to economies of manufactureand numerous other features as will be apparent. from a consideration ofthe specification and drawing of a form of the invention, which may bepreferred, in which:

Figure 1 is an enlarged elevational view of the blast discharging end ofan internal combustion burner showing a primary glass filament and theformation ofpellets when the improper operating conditions for fiberattenuation are present;

Figure 2 is a view similar to Fgure 1 illustrating a method andapparatusof' this invention for effecting an equalization of pressure adjacentthe primary filaments;

Figure 3 is a top plan view of the arrangement shown in Figure 2;

Figure 4 is a view similar to Figure 2 illustrating another form ofmeans for minimizing or eliminating the unequal pressures adjacentprimary filaments at their entrance into an attenuating blast;-

Figure 5 is a top plan viewof the arrangement shown in Figure 4;

Figure 6 is a view similar to Figure 4 wherein a counterstream of gas isdirected into a zone adjacent primary filaments for the purpose ofattaining equalization of pressures adjacent the filaments;

Figure 7 is a top plan view of the arrangement shown in Figure 6;

Figure 8 is a view similar to Figure 6 showing a form of bafile meansutilized for equalizing the pressure adjacent the primary filamentsand'the attenuating zone, and

Figure 9 is a top plan view illustrating the baffle arrangement shown inFigure 8.

While the invention is especially usable in attenuating extremely finefibers from glass filaments, it is to be understood that the principlesof the invention may be utilized to advantage in attenuating other heatsoftenable materials as, for example, fusible rock, slag and"thermosoftenable resins.

One method of attenuating glass or other fiber forming materials tocomparatively fine fibers involves feeding primary filaments, rods orelongated bodies of glass. into an intensely hot, high velocity gaseousblast which functions to soften the advancing filaments and draw orattenuate them into fibers under the inffuence of the blast. Anapparatus for accomplishing this purpose includes a burner 10, theforward portion or outlet end of which is shown in Figure l. The burneris of the internal combustion type shown and described in the U. S.Patent to C. J. Stalego, No. 2,489,243 granted November 22, 1949, havinginternal refractory lined walls capable of withstanding the hightemperatures. of combustion. A fuel and air mixture is delivered intothe rear of the. burner in proper proportions whereby substantiallycomplete combustion takes place within a confined zone of the burner.The burner construction is provided with a restricted orifice ordischarge outlet 12 preferably elongated laterally through which theexhaust or burned gases of combustion are projected at comparativelyhigh velocities providing an intensely hot blast.

One or more primary filaments or rods 14 of glass are arranged to becontinuously advanced or fed'into'the blast by feed rolls (not shown) ina manner whereby the advancing tips of, the filaments. are softened and:drawn into. fibers. It has been found in actual practice-that severalfactorsenter into the successful attenuation of fibers by theblast-burner method and that such factors are critical in nature so thatincommercial practice difficulties may be encountered incorrelating allof such-factors to establish optimum fiber attenuating conditions. If'the filaments are fed into the blast at too slow a rate for the propervolume of glass to be attenuated or if the temperature is too high forthe amount of glass fed into the attenuating zone, then slugs or pelletsof glass are formed on the fibers as illustrated in Figure l, acondition which not only renders the fibers unsuitable for use but thepellets are waste material.

The filaments extending into the blast present impediments to the freeflow of the gases of the blast, setting up unequal pressures on oppositesides of the filament in the direction of movement of the gases so thaton the downstream or lee side of the filament a zone of reduced pressureor partial vacuum is existent while on the diametrically opposite orupstream side of the filament an elevated or increased pressure may beset up by reason of the impingement of the gases against the filaments.Thus the rate of feeding the filaments into the blast and the velocitiesand temperature of the blast must be properly correlated in attainingoptimum conditions for attenuation.

If one or more of these factors deviate or vary from a regulated. modeof operation, the reduced pressure or partial vacuum adjacent thedownstream side of the filament usually results in the blast causing thesoftened filament to move upwardly in a hook-like formation and, as suchportion is moved out of the most efficient zone of attenuation or coreof the blast, the softened material tends to coil up and form smallslugs or pellets. By increasing or equalizing the pressure adjacent thedownstream side of the filaments, the tendency for the softenedfilaments or fibers formed therefrom to coil into pellets is eliminatedor substantially minimized.

The invention provides a method and means for attaining substantialequalization of pressure in the attenuating zone adjacent the primaryfilament through the positioning of a medium at or adjacent thedownstream side of the filament so as to eliminate to a substantialdegree the existence of a partial vacuum in this zone. One form of meansto eliminate or substantially reduce the partial vacuum is illustratedin Figures 2 and 3. One medium utilized for the purpose may be in theform of a baflle, rod or shaft 18 extending substantially horizontallyof the blast and adjacent the downstream side of the filaments 14a. Ithas been found that the placement of the baflie may be advantageouslyemployed at any position between the dotted and full line positionsindicated respectively at 18 and 18. As the baffle 18 is actually in thepath of the'intensely hot gases, it'is preferably formed of refractorymaterial, heat resistant metal, ceramic or any suitable material capableof withstanding the high temperatures and velocities of the gases.

The hot gases of the blast moving in the path or l'ocus indicated by thearrows at 20 function to soften the advancing'tip portions of theprimary filaments 14a which are drawn by'the' blast into taperedsecondary filaments 22 usually referred to as secondaries which aredrawn out or attenuated by the velocity of the blast to form fine fiberswhich are entrained in the blast and may be collected upon acontinuously moving belt (not shown) or other suitable collecting means.

The bafile or member 18 extending transversely of the blast and adjacentthe primary filaments 14a tends to streamline-the fiow'of gases byintroducing an impediment in the path of the gases between adjacentpairs of filaments on-the downstream sides thereof which tends toequalize the pressure in the downstream zone above the softenedsecondary filament portions 22 and substantially eliminates the partialvacuum in this zone.

The battle arrangement is disposed substantially centrally of theblast'which-tends to retard the speed of the gasesat the core oftheblast and eliminates upward movement andhook-like formation of thesecondaries 22; It has been found that the elimination of the hook-likeformation avoids or substantially eliminates the formation of thepelletsor fibers encumbered with the pellets.

, temperature, rate of glass feed, etc.

The baffle arrangement 18 is preferably carried by a supporting means 23adjacent the ends of the baffle such as threaded members 24 which may bemanipulated so that the most effective and efiicient fiber attenuatingconditions may be secured by the proper positioning of the bafiie meansby regulating or controlling the ambient pressure at the zone ofimpingement of the blast upon the heat softenable material.

Figures 4 and 5 illustrate a modified arrangement of bafiie means foraccomplishing the hereinbefore mentioned purposes. In this formelongated baffles 25 of rod-like shape arerespectively disposed invertical planes passing through the several primary filaments 14b and atthe downstream side of the primary filament. The rods or baffles 25 maybe adjusted to a most eflicient fiber attenuating relation as from fullline to dotted line position or at any intermediate position.Furthermore the baffles 25 may be vertically positioned or may beangularly disposed up to an angle of about forty-five degrees withrespect to the general direction of flow of the gaseous blast indicatedby the arrows 20, the angle of inclination of the bafiies 25 withrespect to the filaments 14b as illustrated in Figure 4 being aboutthirty degrees. The individual baffles 25 may be supported by atransversely extending member 27 and may be formed of refractory,ceramic or other material capable of withstanding the high temperaturesof the blast. The baflies serve to minimize or prevent the existence ofsubstantial vacuum on the downstream side of the filaments 14b and henceavoid the formation of pellets or slugs of the glass during fiberattenuation.

Figures 6 and 7 illustrate an arrangement similar to that shown inFigures 4 and 5 wherein tubular bafiles or members 30 are employed anddisposed on the downstream side of the primaries 140. The members 30 arepreferably hollow and may be supported by a manifold 31 adapted to beconnected to a source of air or other gas under pressure for dischargingjets of air or other gas from the outlets or mouths 33 of the tubes 30to equalize the pressure in the zone rearwardly of the filaments 140 toeliminate the formation of slugs of glass and enhance the fiberizationor attenuation of the filaments into fibers under the influence of theintense heat and high velocity of the gases of the blast.

The manifold 31 may be provided with a control means or valve 35 forregulating the rate of discharge of air or other gas from the tubes 30.By this means the pressure established on the downstream sides of theprimary filaments can be adjusted or controlled to secure conditionsfacilitating most eificient attenuation of the fibers thus minimizingthe necessity for critical adjustments of blast The relative positionand angularity of the air discharge tubes 30 may be adjusted withrespect to the primary filaments dependent upon the conditions of glassfeed, blast temperature and velocity in order to secure the mosteflicient operation.

Figures 8 and 9 illustrate an arrangement of plate like baffles or meansfor modifying the direction of flow of gases of the blast to tend towardequalization of pressure and the avoidance of the partial vacuumadjacent the primary filaments 14d on the downstream side. A pluralityof baffles 40 is arranged with a baffle disposed in the gas streamintermediate each pair of primary filaments, the baffles preferablyextending downwardly to approximately the lower boundary of the blast 20and providing means for streamlining or channeling the flow of the gasesto alleviate the partial vacuum otherwise existing in the downstreamzone of the blast rearwardly of the filaments. The bafiles present animpediment sufficient to divert the gases of the blast generally in thedirection of the zones at the rear of the filaments to augment thepressure at said zones for the purpose of eliminating the formation ofhot slugs or pellets of glass during attenuating operation. Theplate-like baffles are preferably positioned directly betweenthesecondaries 22d and serve to avoid interference between adjacentsecondaries during fiber attenuating operations.

The foregoing structural forms are illustrative of means for carryingout the method of equalizing or tending to equalize the pressures on thedownstream sides of primary filaments to facilitate fiber attenuation,and it is to be understood that baffies of different shapes andconfigurations may be employed without departing from the scope of theinvention. For example, the impediment or abutment 18 may be ofdifferent cross-sectional configurations such as rectangular, square oroval and likewise the members 25 shown in Figure 4 may be of other thancircular cross-section and accomplish the stated purposes of theinvention.

The forms of apparatus for carrying out the IllCihOd perform severalimportant functions in improving the attenuating operations. Thepressure equalizing means or bafiles tend to streamline the gas flowfrom the blast between adjacent filaments and secondaries and eliminateor tend to greatly reduce the partial vacuum or zone of reduced pressurenormally existent at the downstream sides of the primary filaments. Theabutments, baffie means, or the discharge of air in the zone rearwardlyof the primaries has the effect of slowing down the blast velocity inthe center or core of the blast which substantially reduces the tendencyof the fibers to be diverted or moved laterally of the center zone ofthe blast. The reduction in velocity at the central zone of the. blastaids in directing or maintaining the secondaries of the filaments in thecentral and therefore the hottest zone of the blast in a manner toattain continuous attenuation of fibers without the formation of theglass pellets or hot slugs.

The retardation of the rate of travel of the central zone or core of theblast, which unimpeded in the zone of highest speed of the gases,eliminates the substantial differential in the velocity of gases at thecentral zone as compared with that of the gases bounding the centralzone, a factor which otherwise influences or tends to divert the path ofthe secondaries into the zone of partial vacuum. By obtainingsubstantially uniform velocities of the gases throughout thecross-sectional area of the blast as is attained by the invention, thesecondaries remain substantially at the central zone of the best eventhough the rate of feed of the primary filaments may vary and thetemperatures and velocity of the gases deviate from predeterminedstandards. Hence these factors, which have heretofore been extremelycritical in obtaining optimum fiber attenuation conditions, may vary toa considerable extent without disrupting fiber attenuation and withoutresulting in the formation of slugs or pellets of unfiberized glass.

It is apparent that, within the scope of the invention, modificationsand different arrangements may be made other than is herein disclosed,and the present disclosure is illustrative merely, the inventioncomprehending all variations thereof.

What I claim is:

1. A method of forming fibers from elongated bodies of fiber formingmaterial including establishing a heating zone of a moving stream of hotgases; of advancing a substantially solidified body of fiber formingmaterial into the heating zone whereby the extremity of the body becomessoftened and attenuated to fiber form by the heat and velocity of themoving gas stream, and of establishing a medium for increasing thepressure of the gases of the blast adjacent the side of the body in thedirection of flow of the gases to modify the direction of movement ofthe softened material during attenuation thereof to fibers.

2. A method of forming fibers from primary filaments of fiber formingmaterial including establishing a heating zone of a moving stream of hotgases; of advancing a substantially rigid primary filament into theheating zone whereby the extremity of the filament becomes softened,

and of establishing a medium increasing the pressure of the gases at theside of the primary filament disposed in the direction of the downstreamflow of the gases to direct the" softened extremity of the filament intothe gas stream during attenuation thereof to fibers under the infiuenceof the velocity of the moving gases.

3: A method of forming fibers from primary filaments of fiber formingmaterial including establishing a heating zone of a' moving stream ofhot gases; of advancing a substantially solidified primary filament intothe heating zone whereby the extremity of the filament becomes softenedand attenuated to fiber form by the moving gas stream, and ofestablishing a medium for substantially equalizing the pressure of gasessurrounding and adjacent the softened extremity of the primary filamentin the gas stream to substantially eliminate tendency of the softenedmaterial to be deflected away from the stream of moving gases.

4'. A method of controlling the formation of fibers produced byattenuation from primary filaments including advancing a substantiallysolidified primary filament into a stream of hot gases in a mannerwhereby the advancing end is rendered soft and flowable', of attenuatingthe flowable portion to fiber formation by the velocity of the gasstream; and of establishing substantial fluid pressure adjacent thesoftened portion of the filament at the side thereof toward thedownstream flow of the gas stream to bias the softened portion of thefilament into the gas stream during attenuation of the softened materialto fibers.

5; A method of eliminating the formation of slugs during the productionof relatively fine fibers by attenuation including'continuously feedingan elongated body of heat softenable material into a stream of hot gasesmoving at relatively high velocity whereby the material is attenuatedinto fibers; and of establishing an impediment in a zone in the gases ofthe blast at the side of the body of material that is downstream withrespect to the direction of flow of the gases for reducing partialvacuum in said zone for controlling the direction of movement of fibersin the attenuating zone of the gas stream.

6. A method of eliminating the formation of slugs during the productionof relatively fine fibers including continuously feeding an elongatedsubstantially rigid body of heat softenable material into a stream ofhot gases whereby the material is attenuated into fiber formation, andof directing an independent stream of fluid into a zone at the side ofthe body in the direction of downstream flow of the gases forestablishing substantially uniform pressure at the attenuating zone ofthe gas stream.

7. A method of producing relatively fine fibers including continuouslyfeeding a body of heat softenable material in a nonflowing state into astream of hot gases whereby the material is softened and attenuated intofiber formation, and of establishing a pressure equalizing mediumin azone at the side of the portion of the material in the gas stream in thedirection of flow of the gases for maintaining the material in the gasstream during attenuation.

8. A method offorming fibers from fiber forming materials including thesteps of establishing a heating zone of moving gases; of advancing asupply of fiber forming material in nonflowing condition into theheating zone whereby the material is'entrained in the moving gas streamto form fibers; and of establishing a medium for augmenting the gaspressure in azone at the side of the advancing portion of material thatisdownstream with respect to the direction of how of the gases andwithin the zone of themoving gases to retard the velocity of the movinggases in the central zone of the stream.

9. A method of attenuatingfibers from heat softenable material includingestablishing a material heating zone provided by a moving stream ofintensely hot exhaust gases; advancing afilament of heat softenablematerial into-the gasstream in adireotion substantially normal to thedirection of movement of thegas stream;-an'd'=ofestab- 8 lishing apressure equalizing medium"- at that side of the filament that isdownstream withrespect to the direction of flow of the gas stream" toefiect a retardation ofvelocity of the gases at the central zone of thegas stream to maintain the attenuation of fibers substantially in thecentral zone of the stream.

10. A method of attenuating fibers from heat softenable materialincluding establishing a material heating zone provided by a movingstream of exhaust gases; advancing a filament of heat softenablematerial into the gas stream in a direction substantially normal to thedirection of movement of the gas stream, and of establishing fluidpressure at the side of the filament that is downstream with respect tothe direction offlow of the gases by directing an independent flow ofgas angularly into the exhaust gas stream to effect a retardation ofvelocity of the gases at the central zone of the exhaust gas stream tomaintain the attenuation of fibers substantially in the central zone ofthe stream.

11. Apparatus for producing relatively fine fibers from heat softenablematerial including,- in combination, a combustion chamber adapted toburncombustible gases in a confined zone, said chamber having arestricted outlet for the extrusion of the hot gases of combustion;means for feeding a filament of fiber forming material into the exhaustgases in a direction normal to the flow of the gases and adjacent theoutlet for attenuation of the filament into fibers, said filamentinterrupting the normal flow of gases of the blast adjacent the filamentestablishing unequal gas pressures adjacent the filament, and means forincreasing the gas pressure at the side of the filament downstream ofthe blast for controlling the movement of the fiber forming materialduring attenuation.

12. Apparatus for producing relatively fine fibers from heat softenablematerial including, in combination, a combustion chamber adapted to burncombustible gases interiorly, said chamber having a restricted throatfor the extrusion of the intensely hot exhaust gases of combustion,means for feeding filaments of fiber forming material into the exhaustgases adjacent the throat for attenuation of the filaments into fibers,said filaments impeding the normal flow of the gases at one side of thefilament establishing unequal gas pressures at opposite sides of thefilament, and means effective at the side of the filament downstream ofthe flow of the gases for establishing increased gas pressure adjacentthe filament for controlling the path of movement of the fiber formingmaterial during attenuation.

13. Apparatus for producing relatively fine fibers from heat softenablematerial including, in combination, a chamber adapted to burn acombustible mixture in a confined zone and having a restricted orificethrough which the gases of combustion are projected as an intensely hot,high velocity blast; means for feeding an elongated body of heatsoftenable material into the blast adjacent the orifice, and baffiemeans'dispos'ed in the stream of gases forming the blast adjacent thebody of material at its zone of entrance into the blast for retardingthe velocity of the gases in the central zone of the blast.

14. Apparatus forproducing relatively fine fibers from heat softenablematerial including, in combination, a chamber adapted to burn acombustible mixture in a confined zone and having a restricted orificethrough which the gases of combustion are projected as an intensely hot,high velocity blast; means for feeding an elongated body of heatsoftenable material into the blast adjacent the orifice, and meansincluding an impediment disposed in the path of flow of the gasesadjacent the body of material at its zone of entrance into the blast forestablishing a moreuniform pressure of gases of the'blast at said zone.

15. Apparatus for producing relatively fine fibers from heat: softenablematerial including, in combination, a chamber adapted to burn acombustible mixture in a confinedlzone' andhaving a restricted orificethrough which the: gases of: combustion: are projected as an intenselyhot,

high velocity blast; means for feeding elongated bodies of heatsoftenable material into the blast adjacent the orifice, said bodiesimpeding the flow of gases of the blast establishing zones of unequalgas pressure adjacent the bodies and means including a plurality ofbaffles disposed adjacent the bodies of material in the path of themoving gases at the zone of entrance of the bodies into the blast forsubstantially equalizing the pressures of gases of the blast at saidzone.

16. Apparatus for producing relatively fine fibers from heat softenablematerial including, in combination, a chamber adapted to burn acombustible mixture in a confined zone and having a restricted orificethrough which the gases of combustion are projected as an intensely hot,high velocity blast; means for feeding an elongated substantially rigidbody of heat softenable material into the blast adjacent the orifice,and a tubular member disposed adjacent the body of material and havingan outlet, said tubular member being adapted to direct a gas underpressure through the outlet into the zone adjacent the body of materialdownstream of the blast for establishing substantially uniform gaspressure in said zone.

17. Apparatus for producing relatively fine fibers from heat softenablematerial including, in combination, a chamber adapted to burn acombustible mixture in a confined zone and having a restricted orificethrough which the gases of combustion are projected as an intensely hot,high velocity blast; means for feeding an elongated substantially rigidbody of heat softenable material into the blast in a direction normal tothe blast and adjacent the orifice, and a tubular member disposedadjacent the body of material and having an outlet, said tubular memberbeing adapted to direct a gas under pressure through the outlet into thezone at the side of the body of material downstream of the blast forincreasing the gas pressure in said zone.

18. Apparatus for producing relatively fine fibers from heat softenablematerial including, in combination, a chamber adapted to burn acombustible mixture in a confined zone and having a restricted orificethrough which the gases of combustion are projected as an intensely hot,high velocity blast; means for feeding an elongated body of heatsoftenable material into the blast adjacent the orifice whereby gases ofthe blast impinge upon the body at one side and set up a zone of reducedgas pressure at the opposite side of the body; means including animpediment disposed adjacent the side of the elongated body in the pathof the moving gases etfective to increase the pressure of the gases atthe zone of reduced pressure, and means for adjusting the position ofthe impediment relative to the body for controlling the extent ofincrease in the gas pressure at said zone.

19. Apparatus for producing relatively fine fibers from glass including,in combination, a chamber adapted to burn a combustible mixture in aconfined zone and having a restricted orifice through which the gases ofcombustion are projected as an intensely hot, high velocity blast; meansfor feeding filaments of glass into the blast adjacent the orificewhereby the filaments obstruct the normal flow of a portion of the gasesof the blast and establish zones of reduced gas pressure adjacent thefilaments; bathe means disposed adjacent the sides of the filaments inthe zones of reduced pressure, and means for adjusting the relativeposition of the bafile means for controlling the gas pressures at thesaid zones.

References Cited in the file of this patent UNITED STATES PATENTS2,489,243 Stalego Nov. 22, 1949 2,515,738 Slayter et al July 18, 19502,578,101 Stalego Dec. 11, 1951

